Telephone system



Apnl 7, 1925. 1,532,888

H. D. GURRIER ET AL TELEPHONE SYSTEM Filed July 15, 1920 2 sheets-sheet 1 huez-T1275:

April 7, 1925. 1,532,888

I H. D. CURRIER ET AL Filed July 15, 1920 2 Sheets-Sheet 2 Patented Apr. 7, 1925.

UNITED STATES .PATENT OFFICE.

HIRAM. n. CURRIEB, AND WILLIAM e, snoer., oe omesso, ILLINOIS, AssIGNoRs 'ro KELLOGG swrrcnoann AND surety oorarANY, or (intenso, ILLINOIS, Aeon.'-

IPORATION OF ILLINOIS.

TELEPHONE SYSTEM. f

Application filed July 15, 1920. iSerial'N'o. 396,401.

T0 all whom it may concer/n:

Be it known that we, HIRAM l). @Unsinn and WILLIAM G. Snom., citizens of the United States of America. residing;` at Chicago, county of Cook., and State of Illinois, have invented certain new and usefullmprovements in Telephone Systemaof which, ythe following is a specification.

@ur invention relates to telephone s vstems and has to do more particularly with systems in which link and trunk circuits are used for interconnecting subscribers lines. such vas toll to toll connections and toll to local connections. and an object of ouiI invention is the provision of an improved circuit arrangement of the above character which will embody desirable features in a simple. efficient and economical tion must be extended to some other point over a toll line and the tell line to the point wanted is found in use. the originalv calling operator must be notified of it and the connection 11e-established at another time. A feature of our invention is the provision of paired jacks for each toll line terminatiugV at-r are actuated to place the second connected' cord (whose plug in the seizure jack) in effective connection with the wanted toll line. and when this condition is established. means automatically' ysend current in both directions to )signal that theline is now available. V

Another feature of our invention is the provision of busy lamps associated with toll lines. one for each multiple toll iacl, which are lighted when a connection is established,

lcord are actuated to sever the-connection and v and seizure lamps which are also provided one `other operator will notuse her seizure jack of that line.

y Still another feature of our invention is the provision of a timing meter for toll connections, so arranged that a contact is closed after a predetermined lapse of time for a few seconds to signal the operator that the time of conversation `is almost over. the contact breaks, means provided 1n the a disconnect signal is `(given.

Still another featureV of our invention is this: Should the toll call fora llocal substation be of special importance and `'the said local station be busy, the-`calling plug of the toll cord lis inserted ina multiple jack of the station, and battery connectedibyl the actuation of a special key will operate means in the local cord which will sever' the` connection and give ther local operator va signal notifying her that extended. l The featuresas outlined above-" aswell as others. will be more fully described in the ensuing specification and appended claims. For a more complete understandingof our invention reference may be` had to thetaccompanying dra-wings.` which illustrate'circuit arrangements which embody the'` tures of our invention,v in whichi Fig. 1 illustrates a toll lcord' circuit of our invention; ,l f 7 Fig. 2 illustrates a local cord-circuit for interconnecting local lines and adapted to operate in connection kwith the toll cord of our invention and two llocal subscribers line circuits; I Fig. 3 illust 1ates, altoll line circuit; and y Fig; 4 schematicallyl a toll line connection. i i

Referring; first to Fig. 3, we illustrate'a toll line circuit TL, which has a linerelav LR, a cut-oit relay CO and line lamp LLv and answering jack J. In addition to the Lapparatus just,described,' we provide a busy lamp control relayr BR, which is energized an urgent .call is being fea-r When when a plug is inserted vinthe answering' jack J of the line to light the busyv lamps [BL to indicate the busy-condition of the associated -ivi'th a seizure jack SJ, and a link line. A seizure lamp control relay SCR is yprovided which is energized When a plugis inserted into the seizure jack SJ to light the seizure signal lamps SSL.y Each end ofthe toll. line has connected to it the above described apparatus.

The toll cord circuit- TC is provided with a toll plug TP and a combination plug CP, the' said plugs being connected by the heavily marked vconductors. The toll end of the cord 'circuit isv iorconnecting to toll lines only and is provided with'v a ringback` key RB, for the usual purposes',

A test relay TE is" also provided, Which is energized when connection is made With a calling toll line but fails to operate When the cord'is control relay LC is also provided' forestale# lisli'n'g the! continuity of the talking concluetors,.for purposes as Will' be more fully hereinafter described. timing meter TM is also provided, as is also a disconnect relay DR, the timing meter being used for timing a' conversat-iomfan'd the relay DRin associa? i tion With the 'meter TMycontrols the termination of conversation at the end of a predetermined period.-

vlistening key LK isK provided Which', When actuated, ycdni'i'e'cts the operators set to the cord conductors.' A double cut-out key OK is also' providedl orthe usual monitoring purposes. AA supervisory relay SR is provided which 1s energized, 'when the disconnect currentis transmitted to-the cord, to close the circuitvl for 'the flashing toll supervisory lamp' TS', giving the operator a disconnect' signal. A

supervisory signal control relay SUYRisE also provided, Which energizes upon the actua-A tionA of'relay SR andv locks up to liold the signal TS in circuit until restored by the actuation of the listening vkey LK. The

right lhand end of the toll cord lcircuit TC,

theco'mbination end,.can be used eitherfor connection to a` toll lline or to a local common battery-line. Itfislprovided' with a su-V pervisory relay SR Vwhich is 'only brought jincircuit When'thel combination cord plug CP is .in the jack of a local line, anda call; ing supervisory signal CL isalso: provided and is" in association iviththe relay SR for the usual supervisory purposes. .A sleeve relay SL is` alsoprovided which is energized when thecombination plugr CP is insented into either a toll or local line, and a repeating coil control relay CR: is also provided, which is energized When connection f f is' niad'e `With' a local line only to connect the s ings a', o, @and d', in circuit.

repeating coil REC, which comprises yvind-` Relay CR re# mainsl atn'orinal awhen connection is made with a toll line, andthe repeating coil REG isnotxconn'ectedfin circuit: A: special tone Ims TO is also providedfor ,purposesas Will be signals S2.

more fully hereinafter described, and a ringing 4key RK is also provided 4u'fhich, When actuated, connects the generator G to ring the call bell of the called yfor substation or signal over a connected toll` line. l V

Referring now tol Fig. 2,V We illustrate a drawing We illustrate a callingl substation lB,.terminatin0 at the exchange in a line circuit L, comprising the usual line relay LR2, cut-'oit relayCO`2, multiple jacks J2 and line The line circuits as illustrated are known as multiple line lamp circu`its,"in

local cord `circuitChand to' the left of the Which aline lzjiin'p is provided for each' linev jack so that When a' call is initiated, a lighted line signal appears atl each of the multiple line' jacks andl any one of a plurality lof op#Y era'tors may seize the calltothe exclusion' of.

operates to connect the"y operators set O to The answeringv su# the cord conductors. pervisory relay AS is also energized upon the energi'zation oit relay TE,-ivhicli relay AS prevents, at this time, the lightingvr oi the supervisory lamp AL'. Upon the insertion of the calling plug CP into the vjack ont'Y the called line, `the ringing control" relay lcomprises an answer--v RC is energized, which relay in turn brings 'about the energization of the sleeve relay SL. The relay RG upon eii'ergizationconnects 'the interruptery T infcir'cuit with the ringing interrupter relay RI, Whichv A'relay RI is intermittently energized and-de-ener? gized to connect the ringinggener'ator G2 through the ringing relay RRvto the cord conductors to operate vtlije call signal at the called substation. A rsupervisory relay SR2 is energized When )the called subscriber answers to' efface the *callin' supervisory Signal cL.l should uw; .Ca-iin Subscribaansiver during the' ringing period, relay RR energlzes to discontinue the application of ringing current, andy if the subscriber g answers during a' silent period, the relay SR2 energizes toopen lthe' ringing circuit'.

When the calling subscriber replaces his receiier after the termination or the vconversation the relayAS is de-ei'iergizedv and consequently the 'link disconnect relay LD is energized andcausesthe disconnection of the cord conductors from the calling" liire Whichreturns the apparatus of the calling subscribersline circuit to" normal. If. the calling subscriber desires toy recall before the plugs have been'l removed from their r'- spec'tive jacks he will be able toactuate hisl associated apparatus to light the line signal S2 because his line circuit has been returned to normal by the previous `action of the link disconnect relay LD. v

A differential relay 280 associated with the cord circuit is provided so that, should the cord circuit C be in use during a conversation between a calling and. called local subscriber and should it happen that one of the talking subscribers was Wanted by a toll operator and that the call Was very urgent7 the toll operator may sever the connection between the two talking local sub-l scribers by applying battery to the sleeve oit the .multiple jack, and thus battery extends to the relay 280. The relay is unbalanced and operatesto close a circuitv for the link disconnect relay LD, which relay is energized and severs the link conductors and also closes the circuit for signal AL. and the op` erator noting the lighted signal takes down the connection, as Will be more fully hereinafter described.

Having described in general the apparatus embodying our invention,lwe Will now de'- scribe in detail the operation of the circuit arrangement as illustrated, and irst in order Will come the explanation ofthe toll apparatus, reference being had to Figs. 1, 3 and 4.

To properly explain our invention, we shall describe the putting through of a call from a local subscriber at place E to a similar subscriber at place G, and shall assume r there are no through lines from E to G, but

that there are toll lines from both E and G to a place F and that the toll operator at E calls the toll operator at F and the latter connects the line from E to F to the line from F to G, Where the toll operator completes the connection.

This is schematically indicated in Fig. 4l, Where B is the local calling line in exchange E, and B the local called line in exchange G.

The call comes to the toll operator at E in the form of a Written' message, stating that subscriber B at. E Wishes to-talk with subscriber B at G. The toll operator has before her a number of toll lines leadingl to F and these terminate both at E and F in circuits like that at TC in Fig. 1. She inserts toll plug TP into the jack J of such a line Whose lamps LL, SSL and BL are all unlighted, closing circuit from vbattery through windings 4-l of relay TE, sleeve contact TP-J, relays BR and CO to ground. Belay CO disconnects line `relay LR. Relay BR closes contact'lO, lighting the busy lamps BL at the various positions. Closed contact 12 of relay TE energizes linkcontrol relay LC by current through contact 15, and LC by contacts 18 and 19 extends the cord conductors, While alternate contact 20 shunts'v out the 'high resistance Winding 5 of TE for purposes hereafter made clear. By key RB the operator now projects ringing current over the toll line to F, operating line relay LB- O circuit TLv line lamp LL,in.'-seit=stlre toll plug of one oil her toll cords in jack J or" the toll line from E, thus closing a circuit from battery through windings l and 5 ot' relay TE, sleeve contacts of plug TP and `jack VJ, conductor T, relay` BR, to ground through relay' CO. Relay CO, upon energization, dis- 'connects relay LR and unlatches contact 2 to efface the line lamp LL. Biel-ay BR upon energization closes its alternate contact 10, lighting the busy lamps BL.

The

busy lamps BL at all positions at F are` thus lighted to indicate the busy condition of the toll jacks d, and their line. Contact 12 of relay TE energizes the link control of LC relay'by current via normal contact 15 of relay DR to ground at contact 12. Bie! lay LC upon energization closes its alternate contacts 18 and 19 to extend the toll cord conductors. TheA closure of. alternate contact 2O of relay LC shunts out the high resistance Winding .5 of relay TE and the circuit of relay TE now extendsfroin batterythrough the low resista-nce Winding 4: of relay TE, alternate contact 2O of relay LC, conductor 6,` the sleeve of plug CP to ground, through-cut-of relay CO. The operator noW actuates her listening key LK and inquires the Want of the calling toll operator at E and learns the call 1 is for G. She inserts the calling plug lCl? into Ithe jack of an idle toll line entending to G which has a toll line circuit similar -to TL, and circuit mayA bev traced through the connecting relay' CR, sleeverelay SL, conductor 23, sleeve. contacts of the connected plug CP and jack oi the called toll line,` through its busy relay andthe cut-olf relay to ground. The relay CR of the toll cord is so adjusted and constructed that it does not operate When the calling plug Cl) is inserted into vthe jack of a toll line, but the busy relay BR and cutoffrelay C() of the toll line circuit do, for

the purpose similar to those already-den scribed and the sleeverelay SL is energized to energize relay 2.4.l Relay 24 thencloses contact26 to extend the cord to the toll line since the relay CR remains atv normal.

`When the calling plug CP is `inserted'in the signal online lamp LL oa circuit TL in a which the toll line ends and inserts the plug TP o one of her cords with results as When theoperator at v.F plugged intothetoll line.

The operator at G nowreceives the number voi' the wanted vsubscriber from the operator connected to the toll line as previously de-y scribed) when said cord is connected to a' local subscribers line, it operates contacts 55, 56 and 57, and bridges the windings a, 7), c and Z of the repeating coil REC across-the cord conductors. The closure of alternate Contact 58 lights calling supervisory lamp CL, the said lamp remaining lighted until lthe called local' subscriber answers. The `operator i'iow actuates her ringing key RK to connect ringing generator G to ring 'the bell at the called substation, and in response to his call signal the subscriber at B removes his receiver from the switch hook and closes an energizing circuit forthe supervisory relay SR, traced from battery `through the upper winding of said relay SR', conductor 61, the winding c of the repeating coil REC, alternate contact 55,l alternate contact 26, the now closed contacts of the ringing key RK, the tip contacts of the connected plug CP and jack J 3, through the substation, back through the ring con' tacts of the connected plug CP and jack J 3, contact key RK, alternate contact 57, winding Z of the coilv REG, conductor 62 to ground through the lower winding of the supervisory relay SR. The relay SR then opens 'normal Contact 60, effacing calling supervisory signal CL. The toll operator at G tellsy the called-tor party at B to hold the line, advises the toll operator at E that she has the party. The operator at E with her plug CP connects with the calling line and rings just as described for the operator at G. Subscriber B answers and the two local ysubscribers are in conversation.

Byv referring'to Fig. 4 the relation of the subscribers lines, cord circuits and toll lines will'be immediately apparent.

, When the subscribers inish their talk, they replace theirreceivers, opening the circuits lof the relays SR, respectively connected to their lines and supervisory lamp CL at E as well as that at G are lighted. Y

The operators at E and G listen in,vfind conversation is linished, withdraw the plugs from the locallines and, before withdrawn ing the toll. plugs of their cords, vdepress their ringing keys RB for a moment.. Suppose the operator at Eoperates her key RB lirst. Alternating current will flow (referring to' Fig: 3) through'plug TP at E, `over the toll line to F, through toll lplugA TP lat F to-circuit TG at F, through winding a of REC, relay SR, winding Z) and back to ground at hey RB at E. Relay rSR n1omentarily energize's andv by contact hfk5 operates relay SUR, which locks, and lamp TS flashes by current through constantly rotating interrupter I. Furthermore, the current from RB at Epasses on through the cord at F over the toll line to G, through the toll plug TP, through winding c of coil REG at G, relay SR there, back through winding b to E, with 'the result `that the lamp TS at G alsoflashes'. The operators at F and G listen in (unlocking relays' SUR) and withdraw the plugs of their cord circuits and all apparatus is at normal.

Let it be assumed that while the subscribers` B and B were conversing, some operator at E had a, `call for exchange G,.which she passes to the operator at F over anidle toll line in a manner obvious from the vpreceding. The operator at Fhas no idle toll line to G at this moment, so she seizes the one B and B are talking over. The operator at F will have answered the call from E with the toll plug TP of a cord pair and c would ordinarily use plug CP to connect to the toll line to G.l For seizure purposes however, a plug TP must be connected to the line to be seized, sothe operator at F- reverses plugs of the cord she is now using, putting the calling plug in the jack of the line from E and TP in a multiple seizure jack of the busy toll line to G. Current then passes from battery through windinvs 4.-5 of relay TE of the seizing cor through the sleeve plug contact, sleeve of seizure jack SJ relay SCR of the busy toll line, its -relay CO to ground. rRelay SCR lights the seizure lamps SSL and other operators waiting for a toll lineto seize; 'are warned 0E. 4Since a combination plug Cl? is already in a jack J of this toll line,ythe

relay TE. of the seizingplug is shunted by -the circuit including relays C R yand SL of the combination plug already in the jack of the toll line to G, and this shunt is low `enough so thatrelay TE of the seizing cord remains inert for the time being, the cord i.

which energizefCircuit or""37 may be 1,5aassaA f traced from ground at 12, contacts 15, 72, conductors 755-74, contacts 75, 58 to battery. LC instantly cuts oil 37, but as the latter is of the slow release type, it fora short time remains energized and holds generator over a circuit that may be traced through alternate contacts 89, 86 and Wind' ings Z) and a of coil REC across the main cord conductors, and this current will pass over the toll line to G and also over the other toll line to E. At E it will cause relay SR to energize, resulting in lamp TS tiashing, and the operator will know the seizure has become elfective, and she Will cut her telephone set in on the line. At G the current Will operate the line relay LR to light lampl LL, if the `operator there has plugged out, Who Will in that case plug in again and take the order from the operator at E, and the second call Will be completed in a Way apparent from the description of the first call.

It Will be observed the energization of relay LC has cut oft tone TO, Whichhas remained on the toll line to E, so that until the seizure did become effective the operator at E, listening in, could assure herself that the holding process was still going on.

Although the foregoing description had the seizing toll plug TP put in a jack to which toll plug TP had been connected, seizure would have Worked equally Well if the seizing toll plug had been put in the seizure jack of a line that had a toll plug in its jack, as in that case the relay TE of the seizing plug Would have been shunted by the lovv Winding 4 ot a previously connected relay TE and TE of the seizing plug Would not have energized till the previous connection was taken down.

It is also to be observed that a toll line can be seized when it is rendered busy by a plug inserted in its seizure jack. In such case the operator, looking for a toll line and noting one with lamp SSL lighted and lamp BL not lighted, will plug into a jack J and effect seizure perfectly Well. J and SJ are interchangeable in function, as are lamps BL and SSL.

Ve will next describe the operation ot the timing meter' TM. Assume the connection between B and B has just beenestablished and conversation is about to coininence. Each toll cord has a Imeter TM and the originating operatoigthe one at E in this case, has charge of the timing o the call. Working under the assumption that the toll time is three minutes, the `instant that the conversation starts, the operator of the toll cord at E starts the timing' meter TW, a clock-Work device, and this meter is' so arranged that at some lapsed period ot time, say tWo minutes and forty vseconds of conversation, the indicator or pointer 86 engages a conducting strip 85, which In fact, jacks closes an energizing circuit for the Warning lamp WL from battery, through the lamp.

VL conducting strip 85 to ground at-the The 'operator' of the co-nf '70` lighted signal WL now actuatesher listenindicator 86. t nected toll c'o-rd circuit TC observing the ing ,key LK to i connect her operators set O to the cord conductorsl and notities the subscribers that their time is almost up,

and this' actuation of the listening key LK-r` closes an energizing' circuit for the relay DR, traced from battery through thevvindf' ing of the relay DR, normal contact 87 of relay DR, conductor 88, alternate contactl 89 of' listening key LK, coiiductoi'90, conducting strip 85, to ground at the indicator f 86. The relay DR, upon energizingopens v its normal contact 15, openingk the` initial@` energizing circuit of relay LC at the no-W open contact 15, but tlierrelay LC is held energized during this twenty second period over a circuit traced from batterythrough t the Winding or' relay LC, conductor 14, al-

ternate contact 15 of relay DR, conductor 91, the conducting strip 85 to ground atvthe indicator 86 of the timing meter TMR The` closing of alternate contact 87 of relay DR establishes a locking circuit for the *saidr `relay DR from battery throughthe Winding of the said relay DR,its alternate contact 87, conductor 92 to ground through the y normal contacts 93 and k94: .of the double cut-out key OK. At the end oft-he twenty second period, the indicator 86 disengages the conducting strip 85,7Which novvv opens the holdingy circuit of'relay LC,Which'relay LC now deenergizes and'opens its alternatel contacts 18 and 19 to destroy` the continuity of the cord conductors, and the connection is thus interrupted. The relay TEris held en-` ergized vvhen the relay LC restores over a substitute circuit, traced' from lbattery through Winding 4 of relayTE, conductor 95, alternate contact 96 of relay DR, con- TS, tracedfrom battery through the inter- .rupter I, through thelainp TS, .conductor A 101, normal contact 102 o1 relay LCv to ground at alternate contact of relay DR.

The constantly rotating interrupter' I noW flashes' the signal TS, notifying vthe operav Vtor that the conversation has beenl inter- ,a

rupted at the end of the three minute period.

The operator may again converse With the subscribers by actuating the key OK, which f energizes and again closes the circuit for relay LC through its contact 15 and LC energizes, andl contacts 18 and 19jagain dass ai@ @hentay of the airing Genaue vtors'so the subscriber-sniay again carry on p l l l through the said relay LS, contact 204, t

the conversation for'an additional period of three minutes. Should the operator not notify the subscribers of the limited period der control of a toll operator -t'o 'break down an existing local connection in favor or a toll *cally llitli such an arrangement 'all toll Acalls can, if desired, be given full pret'- erenc'e over local calls, and the holding of loca-l lines as now vpracticed in man-y eX# changes pending completion of toll calls caribe dispensed with, tlie break-down systein permitting a. toll operator to immediyat'ely secure any wanted local line whaty ductor 202, normal contact 203` of relay LD, sleeve contacts of jack J2 and plug` AP to low vresistance path shun-ts' outthe' high reeyer, whether idle or-bu'sy.'

Assuming that the subscriber B initiates i call,rei'novalv of the receiver energizes the line relay LEZ, which lights line 'signals S2. An

operator inserts answering plug AP into a multiple jack J2 and energizes test relay TE' and the cut-on .relay CO2, by current. traced from battery through the low (200) and high (201) resistance windings of relay TE,

normal contact 203 of relay LD,= the sleevev lockingY circuit vfor the relay TE',y traced l from-battery through the low winding 200 of relay TE, its alternate Contact 245, conground throughthe cut-oli'l relayGO. This sistance winding-1 of relay TE tor purposes as. will presently bedescribed. rEhe closure of alternate Contact 260er relay TE establishes an energizing circuit i'or'the answering supervisory vrelay AS1; traced frombattery through the lower winding of relay AS,-'condu`ctor 2617 normal Contact 247 of relay LD, ring contacts of "the connected plng "AP and jack 'J2 through the'clo'sed contacts of the substation switchhook back through the tip contacts ct the jack J2 and plug APQ' normal contact 2460i relay LD, conducto-r 262, alternate contact 260 of relay' TE; conductor 267 to 'ground through the upper winding of .relay AS,l and the The @laeuft of @enact 204 en erg-ias the leaning any, Ls,- by @naar ground at contact 206. Contacts 207 andy '208 now connect the operators' set O" to the cord. Should a second operator attempt to" answer the initiated call, the' loiywinding of relay TE of the first c'ord prevents relay TE" of the second cord fi'onifoperating by shunt-ing it, and the second operator finds'v she is 'shut out and disconnects. Assuming the connected operator finds leubstation B is waiited,'she tests and5'fiiidiiig it idle inserts calling plu" CB" substation ir ,This energize@ ringing control relay RC current through its windings 209 and 210nori'nal contact 212,- sleeve contacts of plug UP and vjack Jagt@ ground: through cut-off relay CO3. contact 215' of relayl RC enei'gizes sleeye rc' lay SL by Current traced from battery throughthe winding of said relay SL', conmet 215 er may `no and amarga/ping or' and jack J3, to ground through relay G03'. Alternate contact 217 of relay RC locks said relay, tracing from winding 209i,*Contact` 217 normal Contact d19,v normal-contact 221', con! tact v222 yto ground at Contact 223. The closing'of contact 224` of sleeve relay SL locks it to ground through cut-oft relay CO3; The relay SL tipon energiz'atioii opens the energizing circuit vot relay LS," which' ref` stores to open its alternate contacts 207 and 208 to disconnect the operators set O frein the cord conductors. Contact 225 vof the relay RC now connects interri'ipter I to the ringing in'terriipter relay RI; vThe ref; lay RI is thus intermittently energized and cle-energized by interrupter I and ringing current from G2 intermittently rings the bell at B. The calling subscriber at the substation B is also givenan audible signal during the ringing of the called'for 'sub-L vof the receiver opens the energizing circuit .disconnect relay LD" iioinbattery through 'wliich opens the energizing circuit of the EC 'which Arelay Roglc ringing control relay into multiple jackl J3 of g A ,e i 80,

The dosing" of ico ' contact 203 of relay LD,v alternate contactrestores, and upon its restoration its alternate contact 225 is opened to disconnect the interrupter I Ltrom relay Rl, and relay RI now remaining at normal, further application of ringing current is prevented. Answering lamp AL lights and the operator pulls down the plugs.

Assuming the subscriber at the substation B removes his receiver from the switchhook during a ringing period, the combined generator and battery How through the relay RR energizes the said relay RR, which opens contact 221, unlocking relay RC, which latter opens contact 225., disconnecting interrupter I from relay Rl, which prevents further application of ringing current to the called substation B. The closing of normal contacts 227 and 228 now causes the supervisory relay SR2 to energize in an obvious manner by current through substation B. The calling subscriber at the substation B and the called subscriber of the substation B are now in conversation, talking circuit being traced over the heavily marked conductors.

The subscribers completing their conver-` 242, normal contact 240 of the relay AS,

alternate contact 243 of rela-y TE, conductor 244 to ground at alternate contact 223v of relay SL. The relay TE is held energized upon the energization of relay LD over a circuit traced from battery through the upper winding 200 of relay TE, its alter-` nate contact 245, conductor 202, alternate 243 to ground at contact 223. The opening of normal contacts 246 and 247L ot-the relay LD interrupts the cord conductors, thus disconnecting' the said cord circuit from the line ot the calling subscriber. The closing of the normal contact 240 of the relay AS lights answering supervisory lamp AL. The replacing ot the receiver at B opens the energizing circuit ot the supervisory relay SR2, which relay restores and lights calling supervisory lamp CL. The `two supervisory lamps AL and CL are now lighted to noti-ty the operator that conversation has terminated.

Should at this time the subscriber at A' wish to recall be't'ore the plugs have Abeen removed, he again removes his receiver, enersignals AL and CL now withdraws the plug CP. The withdrawal ot plug CP from the jack J3 opens the. locking energizing circuititor the relay SL. Said relay SL restoring to normal opens its alternate contact 223, vhich'opens the circuits for l the relays LD and TE, restoring them to normal, the opening of contact 219 and 'con-l tact 243 extinguishing the supervisory lamps.

The apparatus used in establishing theA above described connection is now at'normal and available for use in establishing other connections.

It will be observed that whenthe operator first inserts plug All into jack J2, differential relay 280 energizes dueto the closure of contact 245, but this does not affect relay LD because conductor 286 is open at 287. when the operator plugs into the called line, current will flow through winding 283 of relay 280 simultaneously with the energization ot relay RC, and since current is alsoflowing through theother winding 282 oi' relay 280 at the same time, relay 280, due to` its differential construction will de-energize and open its ycontact 284 before the contacts 287 and 223.01C relay SL can close to establish an energizing circuit for relay LD whereby relay LD is prevented from operating at this time. f 1

Assuming now that a subscriber as B wishesv to converse' long dist-ance' withv a` local subscriber and that the call lis very urgent. The local line multiple appears before the toll operator, and assuming that the local line wanted is busy, the urgent call will be given preference over the local lconnection. rlhe toll operator now 'inserts'the combination plug of the toll cord. circuit` TC into the multiple ack, as J4, of the called local line that is busy and actuates the cord circuit break-down key CCB and her listenving key LK, vwhich establishes an energizing circuit for the differential relay 2,80 o-il the local cord circuit C that has been used in placing the two local subscribers in conversational circuit. The circuit. is traced from battery .through thenow closedcontact ot' theV key CCB, conductor 110, alternate contact 111 of the listening key LK, conductor 112, the sleeve of the calling plug Cl) ot' the toll cord circuit TC, the/*sleeve of the multiple jack J4 and the sleeve ot the jack J2 and answering plug AP of the local llO cord circuit C, the normal Contact 203 of u the link disconnect relay LD', conductor 202, alternate contact 245 ot the relayTE, conductor 281, through the lett-hand winding 282 ot the rela-y 280 to battery. The relay 280 being a diiterential relay is unbalanced as a circuit extending through the right-hand winding 28,3 from battery, over conductor 214 to ground through the cut-oit relay CO3 ot the line circuit, brings about this unbalancing effect. The said relay 280 actuates and the closure ot its alternate contact 284 .establishes an energizing circuit t'or thelink disconnect. relay LD, traced from v battery through the winding of the relay LD, conductors 241 and 285 to alternate contact 284 of relay 280, conductor 286,A

through alternate ,cont-act 287 to ground at alternate contact 223 of the Vsleeve relay SL. The relay LD upon energization opens its normal ,contacts 246 and 247, thus'interrupting the talking .conductors, severing conversational circuit between the two local subscribers. The closing ot alternatel Contact 284-' ot the relay 280 closes an Aenergizing circuit for the answering supervisory signal AL, traced `from battery, throughkthe lamp AL, conductors 241 and 285, alternate contact- 284 ot relay 280, conductor 286, alternate contact 287 ot relay SL, to ground at alternate Contact 223 ot' Athe said relay SL. Relay LD remains energized and lamp AL lighted until the operator noting the lighted supervisory signal AL, withdraws the answering plug and the calling plug from their respective connected jacks, thus clearing the line circuits of both subscribers, placing `them vin condition so that a conversation may be carried on' between the calling suhscriher and the local subscriber thatthe toll subscriber is urgently seeking. A tone is alsoplaced upon the sleeveot the local jack whenever a calling plug GP .of the toll cord circuit vTC .is linserted into a local jack, the lsaid toney being traced from the said tone T 0, over conductor 23, to the sleeve of. the plug Cf 'so that the local operator or any. ofthe to-ll operators desiring a local subscriber mayv know that the local line is being used for va ltoll call, and this tone is put on the'toll sleeve as long as thetoll calling plug remains in the local line spring jack. y It is also to be noted that it a called local line to which plug CP `is-connected is the one a toll operator urgently wants, the operation of key CCR after the toll operator has plugged into jack J5 ot' the local called line, `will unbalance rela-y 280 (but trom the otherv side), the relay 280 operates, resulting in the local operator pulling down the connection. l

While we have eXplainedour invention as tor a switching station use, it isy by no means limited thereto in its broader aspects, as will =be apparent to one skilled in the art, and in the claims we do not intend to v so limit` ourselves.

Having described our invention what we claim as new and desire to secure by Letters Patent 1s:

kLosanna ally busy and apparatus whereby an Voperator is electrically signalled yto that eti'ect. 4

2. In a telephone trunking system including telephone lines terminating in diierent` exchanges, a line at one ot'fsaid exchanges adapted to receive a double busy condition, and means including supervisory signals whereby a distant exchange operator can tell whether it is singly busy or doubly busy.

3. ln a `telephone trunking system, a telephone line having' two link circuit connection terminals applied to multiple contacts at one end of the Vline for extending said line to other exchanges,'one application being effective and the other ineffective, andv means to automatically render said ineli'ective one effective and to extend signals ,to switchboard operators.

Ll. In a telephone trunking system having two telephone lines each terminating `in `diterent exchanges and effectively connected together, a. third incifeotively .out .in on the connection, and means automatic-ally ,operating when the first two lines terminatingat said ditl'erent exchanges are disconnected to renderL effective the connection kof the third line to a predetermined one of said two lines and to automatically signal over said third line and said predetermined yline.

5. ln a toll line system, a builtup ,toll line switched through at a switching station, means whereby'disconnection at saidswitching station automatically `builds up a diffei1n ent toll linek therethrough.v and transmits signals to bothends ot said different toll line.

6. In a telephone trunking system, a tele-v phone line havingmultiple jacks so connected that one can-be plugged into and used .in a conversation, and al second plug inserted in the other `jack, meansincluding supervisory signals 'for automatically advising associated operators that two plugs are connected to the line, and relay means for the ksecond plug operating automatically when the iirst connection is taken down to change the connections of the plugs circuit.

7. In a telephone system, a local cord circuit connecting two subscribers lines for conversation, said circuit provided with' ,a breakdown apparatusincluding a link diS- connect relay and ak differential relay, la toll cord circuit adapted for connection to one of said lines and also to .the local circuit,

and having means operable to render ,said

apparatus active and secure va ywanted one oi said lines for a toll connection, said link disconnect relay also operable to reeone of said subscribers lines, when lsaid one subscriber replaces his receiver, to permit `said subscriber to initiate another call prior to the physical disconnection of said cord circuit and said Ysubscribers line.

v S In a telephone system including trunk lines, trunk circuits for interconnecting same, busying means for indicating that one of said trunk lines has been connected to, other busying means for indicating that the same said trunk line has been connected to by another of said trunk circuits, the connection of said second trunk circuit' with said trunk line rendered non-effective so long as said first connection exists.

9. In a telephone system including trunk lines, trunlr circuits for interconnecting same, busying means for indicating that onel of said trunk lines has been connected to, other busying means for indicating that the saine said trunk line has been connected to by another of said trunk circuits, the connection of said second trunk circuit with said trunk line rendered non-effective so long as said first connection exists, and means for effecting a connection between said second trunk circuit and said trunk line when said first connection is withdrawn.

10.V In a telephone system including trunk lines, trunk circuits for interconnecting same, busying means for indicating that one of said trunk lines has been connected to, other busying means for indicating that the saine said trunk line has been connected to by another of said trunk circuits, the c0nnection of said second trunk circuitwith said trunk line rendered non-effective so long as said first connection exists, means for effec-ting a connection between said second trunk circuit and said trunk line when said first.

connection is withdrawn, and signaling means for indicating that the said second connection has become effective.

1l.' In a telephone system including trunk lines, trunk circuits for interconnecting same, busying means for indicating that one of said trunk lines has been connected to, other busying means for indicating that the same said trunk line has been connected to nection of said second trunk circuit with said trunk line rendered non-effective. so

long as said first connection exists, and

means for indicating that such a connection has been made, said last means rendered inoperative when said first connection has been withdrawn.

l2. In a telephone system including trunk lines, trunk operators positions, trunk circuits at each of said positions for interconnecting said trunk lines, busying means for indicating that a connection has been made between one of said trunk lines and one of said trunk circuits, busying means for indicating if a. second trunk circuit is connected to the same said trunk line before said first connection is removed, said last connection non-effective but rendered effective when said first busying means are removed.

13. In a telephone system including trunk operators positions, trunk lines between said operators positions, trunk circuits for connecting to said trunk lines, means for busying one of said trunk lines. when a connection is made therewith by one operator, means for additionally busying said trunk line when a secondv trunk circuit is connected to it7 and audible means for indicating to a preceding operator that thesecond opera-l tor has connected to a `busy trunk. v

1i. In a telephone system including trunk operators positions, trunk lines between said operators"positions, trunk circuits for connecting to -saidvtrunk lines to interconnect said operators means for said trunk lines operative when a connection is made with said lines, addi-- tional busying meansfor said lines when a second connection is made therewith, audible means for indicating to preceding open' positions, busying en I ators that a connection has been made with a busy line, and means for `autoiiiatically ini dicating to the preceding operatorsthat they.

are no longer connectedv toa busy linexwhen said first connection is withdrawn. f

l5. A telephone line having multiple aclzs so connected that one can be plugged intov and used in a conversation, land a second plug inserted in the other jacl, meansvfor automatically advising associated operators f that two plugs are connected to the line, rei lay means for the second vplug operating automatically when the first connection is taken down to change the connectionsl ofthe i plug, and means for automatically advising all operators removed. n c

1G. A telephone Aline havingl mult-iple jacks so connected that one can be plugged when one of the plugs has been4 into for conversational use, and a second;l plug inserted in the other ]ack for seizing lthat line forconversational use upon the, re-

moval of said first plug, automatic means `for indicating to associated 0]' ieratorsthat--a line has been connected to by two plugs, and.' automatic means for indicating toxalloperators that one of the nected from said line.

jacks so vconnected that a plug can be insertplugs has been discon ,c "1io, 17.*A. telephone line .having"multiple` ed and employ the line for conversational purposes tothe exclusion of other connections with said multiple jacks, a second Vplug inserted into the other jack, said second connection non-effective upon said line for con.- lversational purposes so long as said first connection remains, automatic `means -for notifying associatedy pperators that said` line has two plugs connected thereto, and auto-` matic' means kfor notifying vall operators when one of the plugs. is removed.

18. A telephone system having multiple jacks so connectedthat one plug may be inserted and used in a conversation, and a second plug inserted in the other jack, automatic means for notifying the operator calling for said line that two plugs are connected to said line and that it isnot vautomatic means for advising the operator at the E exchange when two trunk circuits at the F exchange have been connected to the same trunk line and to indicate that said trunk line is unavailable for vconversation, and automatic means for advising the operator at thevE exchange when one of `said plugs is removed and thatfsaid trunk line' is available for conversation. j

20. In a telephone system including an E exchange, an F exchange, and a Gexcliange,

vmultiple jacks for each or' said exchanges,

trunk circuits atv each exchangaior connection with said multiple jacks, trunk lines appearing in said multiple jacks adapted forl interconnecting said exchanges, automatic means for advising the operator i atthe E exchange when two trunk circuits at the F exchange have been connected to the same trunk line and to indicate `that said trunk line is unavailable for conversation, automatic means for advising the operator* at the E exchange when one of said plugs is removed and that said trunk line is available for conversatiomand automatic means iorindicating to the operator at the Gr exchange thata. connection is desired.

21. In ya telephone y system including a number of exchanges, trunk circuit-s at each exchange, .trunk `lines appearing in multipie jacks at said exchanges and adapted to interconnect said exchanges, automatic means for advising the operator at the preceding exchange when the operator at the intermediate exchange has connected two and asse.'

of her trunk circuits to the .same trunk line and to notify *her that the trunk lines leading to the last exchange arebusy, and automatic means for advising the operator at said 'preceding exchange that the trunk circuit connected to the said trunli'line `lirsty has been removed andvthat the line is available, and means for notifying the operator at the last exchange that acall is awaiting her attention,

22. In a. telephone system including two subscribers lines, a local cord circuit for interconnecting `same in conversational circuit, a toll circuit adapted to b-e connected with one or' saidlines and said local cord circuit, means including a vlink disconnect' krelay and a dii'l'erential relay in 'said cord circuit for vautomatically disconnecting said telephone lines during conversation and operable when said toll circuit is con-y nected to one 'or said subscribers lines, said link disconnect relay also operable to free one of said lines from said cor-d circuitJ when said subscriber replaces his receiver, to permit said subscriber to initiate another call even though a physical connection remains between said one line and said cord circuit. y

23. In a telephone system including telephone lines, a local cord `circuit Jior inter-vk connecting same, a toll circuit i'or connection with one or said lines and a. local cord circuit inteconnecting said lines, means in said local cord circuitflior breaking upa conversation between, local subscribers when said toil circuit is connected to one of said lines, permitting 'the subscriber Vonftlie line to which. said' cord circuit has been connected to converse with a subscriber connected to .said toll circuit.; y,

Signed by us at Chicago, in the county of Cook, and State of Illinois, this l2 day oiV July, i920.

HiiniM i). @Unsinn WILLIAML s. sHULL. 

